Assemblies and apparatus for winding a plurality of elongated elements such as wires, cables or cords on one single spool are known in the art.
As a matter of example, when manufacturing composites of rubber with steel cord, such as tires, the steel cords are very often drawn from a creel, which comprises a large number of spools, e.g. 20 to 150 spools in some embodiments and e.g. 500 to 1000 spools in other embodiments. The great number of steel cords is then guided in parallel in order to be inserted between two layers of rubber. A drawback of such a system is that it takes a lot of time to replace the empty spools by filled spools. Using spools with multiple winding, i.e. where a plurality of steel cords is wound upon one spool, reduces the number of spools in a creel and increases the flexibility of the use of such a creel.
However, the simultaneous unwinding of a plurality of elongated elements from such a single spool, may cause difficulties and the subsequent parallel processing of the plurality of elongated elements may lead to an unacceptable degree of fractures and processability problems.
The unwinding difficulties and the processability problems and fractures during the subsequent treatment may be due to a variation in diameter of the elongated elements during their winding, or may be due to the fact that elongated elements become entangled during their winding, or may be due to the fact that the elongated elements, although wound at the same time on the same spool, take different lengths on the spool. Other difficulties during the unwinding operations are due to different tensions in the individual elongated elements during the winding operation.
GB-B-1 163 983 discloses a method for winding a plurality of elongated elements on one single spool whereby it is aimed at keeping the winding lengths of the elongated elements substantially equal to each other despite some variations in diameter of the elongated element. The solution used to obtain substantially the same lengths is to increase the tension in elongated elements with an increased diameter in order to reduce the winding diameter and to decrease the tension in elongated elements with a decreased diameter in order to increase the winding diameter. A separation comb is mounted upstream the winding spool in order to avoid disentanglement of the neighboring elongated elements.
EP-A-0 780 333 discloses an assembly for winding multiple elongated elements on a spool, where the tensions in the elongated elements are kept substantially constant and equal. In order to obtain constant and equal tensions, the assembly comprises following parts:                a set of independently driveable capstans, one for each individual elongated element to be wound;        a single spool where the plurality of elongated elements are to be wound;        first monitoring means for measuring the tensions of each individual elongated element of a subgroup of the plurality of elongated elements;        first control means for steering individually the revolution speed of the capstans driving the elongated elements of the subgroup such that said tensions remain substantially constant and substantially equal to each other.        
Before their winding on the spool, a comb is used to prevent the wires from entangling with each other and from jumping over each other.
So the prior art has provided solutions both for keeping the lengths equal and the tensions constant in the elongated elements to be wound.
Despite these solutions problems are still experienced in determined circumstances when unwinding the plurality of elongated elements at the same time. More particularly, when unwinding, some of the elongated elements show unacceptable large sags. These sags may lead to entanglement with the neighboring elements or to wear or pollution of the sagged elements when these elements drag over the floor of the unwinding shop. Still another problem is that the ultimate product, e.g. a rubber strip with the elongated elements may show some unacceptable wrinkles.